The use of wireless or mobile communication devices has increased greatly in recent years. Mobile and cellular telephones have enabled mobile station users to roam over large geographic areas while maintaining immediate access to telephony services. Mobile stations include portable units, units installed in vehicles and fixed subscriber stations. Mobile stations comprising cellular telephones or wireless handsets are operable in cooperation with cellular, GSM and/or Personal Communications Services (PCS) communications systems among others. Cellular communication systems (wireless carriers) typically provide service to a geographic market area by dividing the area into many smaller areas or cells. Each cell is serviced by a radio transceiver (i.e., a transmitter-receiver base station or cell site). The cell sites or base stations may be connected to Mobile Telephone Switching Offices (MTSOs) or Mobile Switching Centers (MSCs) through landlines or other communication links, and the MTSOs may, in turn, be connected via landlines to the Public Switched Telephone Network (PSTN).
In a multi-service-provider wireless communication environment, such as a cellular network, multiple service providers or carriers may operate in a given geographic area, for example, a metropolitan area. Each carrier will have its own “geographic network” in that area, and will be assigned a unique operational “frequency” or “channel” (which may comprise multiple frequencies or a band of frequencies) for that geographic area. The service providers may have other geographic networks in other geographic areas. However, in those other geographic areas the service providers may be assigned different frequencies. Furthermore, cellular services in different parts of the world operate on different frequency bands. For example, North American cellular wireless networks typically operate in the 824 MHz to 894 MHz frequency band (often referred to as the 850 MHz band) as well as the 1850 MHz to 1990 MHz frequency band (often referred to as the 1900 MHz band). By contrast, Europe and Asia use the 900 Mhz and 1800 Mhz frequency bands.
When a mobile device, such as a GSM device, is taken to a different country, the device will attempt to locate its home network and will likely fail. The device will then scan for other networks that it is able to detect. Typically, frequency scanning when unable to locate the home network often requires a significant amount of time and can consume a significant amount of power, usually from the mobile device's battery.
Further, it is often preferable to scan for particular carrier frequencies when outside of the home network since different carriers have preferred arrangements with other carriers. U.S. Pat. No. 6,397,064 to Bridges et al. describes an intelligent roaming system with over the air programming. Bridges et al. teaches a system comprising a database, a generator and a data providing device. The database stores preferred wireless carrier identities for a plurality of market areas. The generator generates a list of preferred wireless carrier identities and the list is transmitted to the wireless device by the data providing device.
U.S. Pat. No. 6,223,042 to Raffel provides a method of intelligent roaming using network information. Raffel teaches a wireless device using a search schedule that has been optimized using network information, such as the last location of the device. The search schedule can then be optimized by predicting the next location of the device.
U.S. Pat. No. 6,564,055 to Hronek teaches updating an intelligent roaming database (IRDB). Hronek discloses a method and apparatus to maintain different IRDBs or preferred roaming lists in a mobile handset. A wireless carrier code list is selected based on an individualized aspect of the device such as location or time of day. Movement of the wireless device to a new location may trigger a download of an updated roaming list.
A solution or an improved solution to one or more of the above problems is desired.